The present invention relates generally to a vacuum process system, such as a thin-film deposition process system for depositing, e.g., a metal thin film, a silicon oxide film or a silicon film.
In a typical process for producing a semiconductor integrated circuit, a metal or metal compound, such as W (tungsten), WSi (tungsten silicide), Ti (titanium), TiN (titanium nitride) or TiSi (titanium silicide), is deposited to form a thin film, in order to form a wiring pattern on a semiconductor wafer serving as an object to be processed or in order to fill in a recessed portion between wiring parts or the like.
As methods for forming a metal thin film of this type, there are known three methods, such as the H2 (hydrogen) reduction process, the SiH4 (silane) reduction process and the SiH2Cl2 (dichlorosilane) reduction process. Among these processes, the SiH2Cl2 reduction process is a method for forming a W or WSi (tungsten silicide) film at a high temperature of about 600xc2x0 C. using, e.g., dichlorosilane, as a reducing gas in order to form a wiring pattern. The SiH4 reduction process is a method for forming a W or WSi film at a low temperature of about 450xc2x0 C., which is lower than that in the SiH2Cl2 reduction process, using, e.g., silane, as a reducing gas in order to similarly form a wiring pattern. The H2 reduction process is a method for depositing a W film at a temperature of about 400xc2x0 C. to about 430xc2x0 C. using, e.g., hydrogen, as a reducing gas in order to fill a recessed portion in the surface of a wafer, such as a recessed portion between wiring parts.
In all of the above described cases, a gas, such as WF6 (tungsten hexafluoride), is used as a process gas.
A typical vacuum process system for forming such a metal thin film is shown in FIG. 11. In the vacuum process system shown in FIG. 11, a supporting table 4 of, e.g., a thin carbon material or an aluminum compound, is provided in a cylindrical vacuum process container 2 of, e.g., aluminum. Below the supporting table 4, a heating means 8, such as a halogen lump, is arranged via a transmission window 6 of quartz. Then, a semiconductor wafer 1 is mounted on the supporting table 4. The peripheral portion of the wafer 1 is held by a vertically movable clamp-ring (a presser member) 10 to be fixed to the supporting table 4. A shower head 13 is provided so as to face the supporting table 4. A large number of gas nozzles 12 are formed in the bottom of the shower head 13 so as to be distributed substantially uniformly.
Heat rays from the heating means 8 pass through the transmission window 6 to reach and heat the supporting table 4 to indirectly heat the semiconductor wafer 1, which is arranged thereon, to maintain the temperature of the semiconductor wafer 1 at a predetermined temperature. Simultaneously, a process gas of, e.g., WF6 or H2, is uniformly supplied onto the surface of the wafer from the gas nozzles 12 of the shower head 13 which is provided above the supporting table 4, so that a metal film of W or the like is formed on the surface of the wafer.
By the way, in the thin-film deposition process on the semiconductor wafer, the in-plane uniformity of the thickness of the film must be maintained to be high from the point of view of the improvement of the electrical characteristics and yields of the device. In the system with the above described construction, the process gas injected from the gas nozzles 12 of the shower head 13 spreads outside uniformly while flowing downwards, to be discharged from an outlet which is arranged below the periphery of the supporting table 4.
In this case, the clamp-ring 10 can not avoid slightly disturbing the flow of the process gas in the peripheral portion of the wafer although, its thickness is only several millimeters. Therefore, the thickness of the film deposited on the peripheral portion of the wafer tends to be smaller than that on the central portion of the wafer, so that there is a problem in that the uniformity of the thickness is bad.
In particular, there is a problem in that the thickness of the film in the central portion of the wafer is greater than that in the peripheral portion thereof to greatly deteriorate the uniformity of the thickness of the film under supply-limited conditions that the thin-film deposition rate depends mainly on the concentration of the gas, although the above described uniformity of the thickness of the film does not so deteriorate under reaction-limited conditions that the thin-film deposition rate depends mainly on a process temperature. Therefore, although various ways for distributing the flow rate of the process gas supplied from the shower head are carried out, the relationship between the flow rate of the gas and the thickness of the film is very delicate, so that the optimum relationship has not been obtained.
Taking account of the above described problems, the present invention has been made in order to effectively solve the problems. It is an object of the present invention to provide a vacuum process system capable of improving the in-plane uniformity of the thickness of a film by causing a shower head part to have a proper distribution of gas feed rate.
In order to solve the above described problems, the present invention provides a vacuum process system comprising: a vacuum process container having therein a supporting table for supporting thereon an object to be processed; a presser member for pressing the top surface of the peripheral portion of the object to fix the object to the supporting table; and a shower head part which is provided so as to face the supporting table and which has a number of gas nozzles in the bottom face thereof, wherein if the bottom face of the shower head part is divided into a facing portion, which faces the inner peripheral edge of the presser member, and a non-facing portion other than the facing portion, the bottom face of the shower head part is formed so that the gas injection quantity per unit area of the non-facing portion is substantially uniform and so that the gas injection quantity per unit area of the facing portion is greater than that of the non-facing portion.
Thus, the gas injection quantity per unit area from the shower head part is substantially uniform in the non-facing portion, and the gas injection quantity per unit area in the facing portion is greater than that in the non-facing portion, so that the thin-film deposition in the central portion of the object to be processed can be suppressed to improve the uniformity of the thickness of the film on the whole object to be processed.
In this case, in order to increase the gas injection quantity per unit area from the shower head part, the diameter of the gas nozzles in a corresponding portion may be greater than the diameter of the gas nozzles in other portions, or the density of the gas nozzles in a corresponding portion may be greater while the diameter of the gas nozzles is set to be the same. Furthermore, the non-facing portion may exist inside and outside of the facing portion in the bottom face of the shower head part.
According to another aspect of the present invention, the bottom face of the shower head part has a substantially annular region, in which the gas injection quantity per unit area is greater than those in other regions, and the annular region is formed substantially directly above the inner peripheral edge of the presser member for fixing the object to the supporting table, along the shape of said inner peripheral edge. In a region inside of the annular region, the gas injection quantity per unit area is substantially uniform and smaller than that in the annular region. Moreover, a region, in which the gas injection quantity per unit area is substantially uniform and smaller than that in the annular region, may be provided outside of the annular region. In this case, the gas injection quantity per unit area in the region inside of the annular region may be substantially the same as that in the region outside thereof.